The use of anti-free-flow devices with medical pumps is well known in the art. When a fluid is being infused into a patient, it is usually desirable for the rate of flow to be regulated. It is disadvantageous in many circumstances to have a condition, commonly referred to as free-flow, in which flow into the patient is controlled solely by the force of gravity. Such conditions can result in a large volume of solution being infused into a patient over a very short period of time. Due to medical conditions or medication contained in the infused solution, a free-flow condition can pose health concerns to a patient. In some situations it can even result in the death of the patient.
Because of these concerns, numerous devices have been developed to regulate free-flow in medical pumps. For example, several different anti-free-flow devices are shown in U.S. Pat. No. 7,150,727, which is incorporated herein by reference. FIG. 13E of the '727 patent shows an in-line occluder disposed in tubing which is mounted on an existing enteral feeding pump. The infusion set includes a drip chamber which anchors one side of the tubing upstream from the pump rotor and an in-line occluder/connector which is used to mount the other side downstream from the pump rotor. The drip chamber and the in-line occluder/connector keep the tubing in tension against the pump rotor so that rotation of the rotor pumps fluid through the infusion set.
One challenge with the use of anti-free-flow devices is retrofitting presently existing pumps. While newer pump models are typically designed to accommodate anti-free-flow devices, pumps that are already in existence may lack such structures. One concern with occluders used with some existing pumps is that a free-flow condition can occur if the infusion set is not properly mounted in the pump. For example, if the occluder is mounted in a mounting structure and moved into an open position to allow flow but the infusion set is not properly wrapped around the rotor of the pump, there is nothing to control the rate of flow through the infusion set.
One solution to this problem has been the use of in-line occluders such as that shown in the '727 patent. An in-line occluder is placed and designed to prevent free-flow unless sufficient force is developed to expand the tubing sufficiently to allow flow past the occlude, or for an external structure to apply force to the infusion set and thereby open a channel between the infusion set and the occluder.
One problem with in-line occluders is that many older enteral feeding pumps develop relatively low pumping pressures. Because of this, the pumping pressure is occasionally inadequate to overcome the occluder or requires sufficient force that the pump inaccurately determines that there is an undesired occlusion downstream from the pumping mechanism. This causes the generation of an alarm which requires the response of medical personnel to determine that the tubing is in fact not occluded. These nuisance alarms waste the time and effort of medical personnel and unnecessarily disrupt the infusion process.
For example, as shown in FIG. 1, a known occluder 1 is disposed in the tubing 2 of an infusion line and mounted in an existing pump 3 as generally done with pumps such as the pump 3. The tubing is held in tension at one end by a drip chamber 4 at one end and by a connector 5 associated with the occluder 1 at the other. Between the drip chamber 4 and the connector 5, the tubing is wrapped about a pump rotor 6 which engages the tubing to drive a solution through the tubing.
The occluder 1 is advantageous over many other occluders because it will prevent flow through the infusion tubing if the tubing is inadvertently removed from the pump rotor. Other occluders, such as some pinch clip occluders, are opened when the tubing 2 is mounted on the pump and will not close if the tubing becomes loose.
One issue with the occluder 1 configuration is nuisance occlusion alarms. Many older pumps, such as the pump 3, have relatively low pumping power and will detect on undesired occlusion downstream based simply on the pressure needed to bypass the in-line occluder. Thus, it is desirable to have an occluder mechanism which will allow flow without nuisance alarms when the infusion set is properly mounted on the pump, and which will prevent a free-flow condition through the line if the tubing comes off the pump rotor or is otherwise not properly engaging the rotor.
While consideration has been given to simply opening the occluder when the infusion set is mounted on the pump, this still leaves open the risk of a free-flow situation. If the infusion line were inadvertently removed from around the rotor, the rotor would no longer act on the infusion line to control fluid flow. Thus, a free-flow situation could develop, potentially injuring the patient. Thus, there is a need for an apparatus and method for providing protection against a free-flow condition while avoiding nuisance alarms.